Abstract: The red pine bast scale, Matsucocous koraiensis Young et Hu, is a pest of Korean pine (Pinus koraiensis) widely distributed over the virgin forests in the eastern mountains of the Heilongjiang and Jilin provinces. In Fenlin district the Korean pine bast scale has one generation a year and overwinters in the 1st instar. After overwintering the 2nd inster larval stage is a chiefly injuring period. The adult emerges in early June and become abundant in mid-June. Reproduction is sexual, but we observed that one of the females produced eggs before copulation. On an average, each female oviosits about 96 eggs. The young larva hatches in the later part of June and becomes abundant in mid-July. The Korean pine bast scale insects mainly in the virgin forest of the Korean pine distributed on the southern or south-western slope. Eight blocks of the younger pine plantation were recently investigated, but no bast scale was found. Some scale insects have been inoculated against the plantation, but whether they could overwinter or not must be determined by further observation. Aphislions and ants are the important natural enemies which considerably control the population density of this pest.